Aromatic polyamide resins have excellent properties of heat resistance, film formation and toughness, and they are widely used as functional engineering plastics.
However, since their solubility in solvent is poor, aromatic polyamide resins are problematic in that their workability is not so good when they are used as films or adhesive layers. Some amide solvents may dissolve aromatic polyamide resins, but, in general, their boiling point is high and their evaporation rate is low, and therefore, the problem with them is that the solvent removal in film formation with them is difficult. As a result, the solvent used often remains in the films or adhesive layers of conventional aromatic polyamide resins, and in case where the solvent has remained therein, it has significant influences on the physical properties such as adhesiveness to substrates and heat resistance of the resin films or adhesive layers. Moreover, in case where films or adhesive layers of conventional aromatic polyamide resins dissolved in amide solvents are formed on organic substrates, there occurs still another problem in that the amide solvents of high solubility often corrode the surfaces of the organic substrates.
In view of these situations, polyamide resin-containing varnish is desired, which is free from the problems noted above and from which the solvent removal is easy during film formation to give films and adhesive layers with little solvent remaining therein.